This invention relates generally to diagnostic ultrasound systems. In particular, the present invention relates to method and apparatus for obtaining a volumetric scan of a periodically moving object within a body.
A current challenge exists to perform a multidimensional ultrasound scan of a quickly, and more or less rhythmically, moving object within a body, such as a fetal heart. Currently, volume transducers having a conventional one-dimensional (1D) array, which is mechanically moved in the elevation direction, as well as electronically steered 2D arrays, may be used for the acquisition. This technique makes it possible to acquire pyramid-shaped volume data sets. To image the fetal heart, high frame rate acquisitions are necessary, no matter whether 2D or 3D data sets are being acquired. For acquiring 3D data sets in real-time, one limitation is the constant speed of sound at 1540 m/s; this limits the amount of data to be acquired per second and thus these acquisitions are a tradeoff between frame rate and image quality. To acquire and achieve high frame rates, the line density has to be decreased, which significantly impairs lateral and elevation resolution.
One approach is to perform ECG-triggered volumetric acquisitions as described in U.S. Pat. No. 5,159,931 to Pini, Nov. 3, 1992, which is hereby incorporated by reference in its entirety, which works well when imaging the adult heart, but is generally not available for the fetal heart due to absence of an appropriate fetal ECG signal. Alternatively, one may acquire data of several heart cycles at several fixed positions which are recorded with a position sensor, and obtain cardiac motion information via Fourier transform methods as described in Nelson et al, “Three Dimensional Echocardiographic Evaluation of Fetal Heart Anatomy and Function: Acquisition, Analysis, and Display”, J Ultrasound Med 15:1–9, 1996, which is hereby incorporated by reference in its entirety. Another problem is experienced when imaging a fetal heart during early pregnancy with 2D fetal echocardiography, when the relationship between fetus and amniotic fluid allows a lot of movement. If the fetus is very active, it may be time consuming or impossible at the time of the scheduled exam to acquire sufficient cardiac data.
Thus, a system and method are desired to obtain multidimensional data sets of a quickly moving object within a body that addresses the problems noted above and others previously experienced.